Wideband remote unit for distributed antenna system

ABSTRACT

Certain aspects involve a wideband remote unit. The wideband remote unit can include one or more antennas and an analog-to-digital converter (“ADC”). The antenna can receive wideband signals. The wideband signals can include an uplink RF signal and a leaked downlink RF signal. The uplink RF signal can have an uplink signal power at or near a noise level. The leaked downlink RF signal can have a downlink signal power greater than the uplink signal power. The ADC can convert the received wideband signals to digital RF signals representing the uplink signal and the downlink signal. The wideband remote unit can transmit the digital RF signals to a unit of a DAS that is in communication with a base station.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/631,798, titled “WIDEBAND REMOTE UNIT FORDISTRIBUTED ANTENNA SYSTEM” and filed on Jun. 23, 2017, which is acontinuation application of U.S. patent application Ser. No. 14/686,415,titled “WIDEBAND REMOTE UNIT FOR DISTRIBUTED ANTENNA SYSTEM” and filedon Apr. 14, 2015, which claims priority to, and the benefit of, U.S.Provisional Application Ser. No. 61/979,948, filed on Apr. 15, 2014 andtitled “Wideband Remote Unit for Distributed Antenna System,” thecontents of which are each incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to telecommunication systemsand more particularly (although not necessarily exclusively) to widebandremote units for distributed antenna systems.

BACKGROUND

A distributed antenna system (“DAS”) can be used to provide wirelesscommunications coverage in a variety of environments, particularly inlarge structures such as office buildings, convention halls, airports,stadiums, and the like. A DAS can include one or more head-end units(e.g., master units) that are communicatively coupled to one or morebase stations. A DAS can also include multiple remote units that arecommunicatively coupled to each head-end unit. The remote units, each ofwhich can include one or more transceivers and antennas, can bedistributed across a coverage area. The remote units can transmit thedownlink signals to mobile phones or other terminal devices withincoverage areas serviced by the remote units.

Remote units for a DAS may use large amounts of electrical power and mayhave a large physical size. For example, the power requirements and sizeof a remote unit may be increased if the remote unit includes extensiveanalog circuitry for down-converting or otherwise modifying receivedanalog signals prior to generating a digitized representation ofcommunication channels of interest.

The power requirements and size of a conventional remote unit may alsobe increased by using multiple RF transceivers in a DAS to transmit andreceive signals in multiple frequency bands. For example a remote unitmay include a first RF transceiver with associated analog circuitry forcommunicating signals in an Advanced Mobile Phone System (“AMPS”) band,a second RF transceiver with associated analog circuitry forcommunicating signals in a Personal Communications Service (“PCS”) band,and a third RF transceiver with associated analog circuitry forcommunicating signals in an Advanced Wireless Services (“AWS”) band,etc. One or more of the power requirements and physical size of a remoteunit may increase costs associated with manufacturing or installing theremote unit.

SUMMARY

The present disclosure describes devices, systems, and methods involvinga wideband remote unit for a distributed antenna system (“DAS”).

In some aspects, a method is provided. The method can involve a widebandremote unit receiving, via an uplink path, wideband signals that includean uplink RF signal and a leaked downlink RF signal. The uplink RFsignal can have an uplink signal power at or near a noise level of thewideband remote unit. The leaked downlink RF signal can have a downlinksignal power greater than the uplink signal power. The leaked downlinkRF signal can be a downlink RF signal that is transmitted by the remoteunit and received by an antenna of the remote unit. The method can alsoinvolve converting, by the wideband remote unit, the received widebandsignals to digital RF signals that represent the uplink signal and thedownlink signal. The method can also involve transmitting, by thewideband remote unit, the digital RF signals to a unit of the DAS fortransmission to a base station by the unit.

In other aspects, a wideband remote unit is provided. The widebandremote unit can include one or more antennas and an analog-to-digitalconverter (“ADC”). An antenna of the wideband remote unit can receivewideband signals. The wideband signals can include an uplink RF signaland a leaked downlink RF signal. The uplink RF signal can have an uplinksignal power at or near a noise level of the wideband remote unit. Theleaked downlink RF signal can have a downlink signal power greater thanthe uplink signal power. The ADC can convert the received widebandsignals to digital RF signals representing both the uplink signal andthe downlink signal. The wideband remote unit can transmit the digitalRF signals to a unit of a DAS for transmission to a base station.

In other aspects, a DAS is provided that includes one or more widebandremote units and a unit that can communicate with a base station. Thewideband remote unit can receive wideband signals. The wideband signalscan include an uplink RF signal and a leaked downlink RF signal. Theuplink RF signal can have an uplink signal power at or near a noiselevel of the wideband remote unit. The leaked downlink RF signal canhave a downlink signal power greater than the uplink signal power. Thewideband remote unit can convert the received wideband signals todigital RF signals representing the uplink signal and the downlinksignal. The unit can receive the digital RF signals from the remoteunit. The unit can transmit an uplink signal corresponding to one of thedigital RF signals to a base station. The unit can mitigate anotherdigital RF signal corresponding to the leaked downlink RF signal.

These illustrative aspects and features are mentioned not to limit ordefine the disclosure, but to provide examples to aid understanding ofthe concepts disclosed in this application. Other aspects, advantages,and features of the present disclosure will become apparent after reviewof the entire application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting an example of a distributed antennasystem (“DAS”) that includes wideband remote units according to oneaspect of the present disclosure.

FIG. 2 is a block diagram depicting an example of a wideband remote unitof the DAS from FIG. 1 according to one aspect of the presentdisclosure.

FIG. 3 is a block diagram depicting an example of a processing module ofa remote unit from FIG. 2 according to one aspect of the presentdisclosure.

FIG. 4 is a block diagram depicting an example of a unit of the DAS fromFIG. 1 according to one aspect of the present disclosure.

FIG. 5 is a block diagram depicting an example of a non-duplexerisolation sub-system of the unit from FIG. 4 that includes aconfigurable filter according to one aspect of the present disclosure.

FIG. 6 is a block diagram depicting another example of a non-duplexerisolation sub-system of the unit from FIG. 4 that includes acancellation sub-system according to one aspect of the presentdisclosure.

FIG. 7 is a block diagram depicting another example of a non-duplexerisolation sub-system of the unit from FIG. 4 that includes anattenuation sub-system according to one aspect of the presentdisclosure.

FIG. 8 is a graph depicting an example of frequency response associatedwith a wideband remote unit from FIGS. 1 and 2 according to one aspectof the present disclosure.

FIG. 9 is a diagram depicting an example of wideband remote unitsdeployed in a configuration that can be used formultiple-input/multiple-output operation according to one aspect of thepresent disclosure.

FIG. 10 is a flow chart depicting an example of a process for using awideband remote unit from FIGS. 1 and 2 to obtain wideband uplink dataaccording to one aspect of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates to a wideband remote unit for adistributed antenna system (“DAS”). A wideband remote unit can includeany remote unit for a DAS that is configured to generate digitized RFuplink signals from analog uplink RF signals that are received atfrequencies over a wideband spectrum (e.g., 200 MHz to 3 GHz). Awideband spectrum can include a spectrum including frequency bandsassociated with multiple types of telecommunication providers (e.g.,code division multiple access (“CDMA”) systems, Long Term Evolution(“LTE”) systems, etc.). The wideband remote unit can transmit thedigitized RF uplink signals to a head-end unit or other suitable unit ofthe DAS.

In some aspects, the wideband remote unit can perform some analog andsignal processing. The wideband remote unit can be limited totransmitting signals of interest, receiving signals of interest, andtransporting the signals to a central unit in a DAS for processing(e.g., a head-end unit, an expansion unit, etc.). The wideband remoteunit can be implemented in a manner that allows the wideband remote unitto have one or more of a smaller size or lower power requirements ascompared to other remote units.

In some aspects, the wideband remote unit can be implemented withoutfrequency translation circuitry. For example, the wideband remote unitcan include a high-speed analog-to-digital converter (“ADC”) that cansample signals at a sufficiently high sampling rate that allows thewideband remote unit to omit down-conversion circuitry for converting RFsignals to intermediate frequency (“IF”) signals.

In additional or alternative aspects, the wideband remote unit can beimplemented without isolation circuitry for isolating uplink signalsfrom downlink signals. For example, an ADC of the wideband remote unitcan have a sufficiently wide dynamic range to digitally representlow-power uplink signals in the uplink path and high-power downlinksignals that leak to the uplink path. Digitally representing signalsover a wide dynamic range can allow a head-end unit or other suitablehigh-power unit in the DAS to attenuate leaked downlink signals in theuplink path. Using a head-end unit or other suitable high-power unit inthe DAS rather than the remote unit to attenuate leaked downlink signalsin the uplink path can limit the amount of circuitry required by theremote unit.

In some aspects, the wideband remote unit can be used withoutspecifically designing or otherwise configuring the wideband remote unitfor operation with a given telecommunication standard, frequency band,or other telecommunication technology. For example, the wideband remoteunit can include a wideband receiver that can be used to receive signalsin multiple frequency bands.

Detailed descriptions of certain examples are discussed below. Theseillustrative examples are given to introduce the reader to the generalsubject matter discussed here and are not intended to limit the scope ofthe disclosed concepts. The following sections describe variousadditional aspects and examples with reference to the drawings in whichlike numerals indicate like elements, and directional descriptions areused to describe the illustrative examples but, like the illustrativeexamples, should not be used to limit the present disclosure. Thevarious figures described below depict examples of implementations forthe present disclosure, but should not be used to limit the presentdisclosure.

FIG. 1 is a block diagram depicting an example of a DAS 102 thatincludes wideband remote units 108 a-n according to one aspect. The DAS102 can communicate signals between one or more base stations 101 orother transceiver devices (e.g., repeaters) and terminal devices in oneor more coverage zones serviced by the DAS 102. Terminal devices can beelectronic devices used to communicate one or more of voice and data viaa telecommunication system, such as (but not limited to) mobile phones.

The DAS 102 can include one or more units 104. Examples of a unit 104include a head-end unit, a base station router, or other suitable unitthat can communicate with a base station. In some aspects, the unit 104can be a head-end unit or other suitable unit that can communicate withone or more base stations 101 or other transceiver devices incommunication with the DAS 102. A head-end unit can include, forexample, an optical transceiver that transmits optical signals to thewideband remote units 108 a-n. The head-end unit or other suitable unit104 can communicate with remote units 108 a-n in different coveragezones of the same DAS 102. In additional or alternative aspects, theunit 104 can be included in a base station router or other suitabledevice that can communicate signals between one or more base stations101 and one or more head-end units. In additional or alternativeaspects, the unit 104 can be included in an extension unit or othersuitable unit that can communicate signals between one or more head-endunits and the wideband remote units 108 a-n.

The DAS 102 can also include remote units 108 a-n having respectivewideband RF transceivers 110 a-n. Each of the wideband remote units 108a-n can include transceiver devices that can include or becommunicatively coupled to one or more antennas. One example of a remoteunit is a universal access point. A DAS 102 can include any number ofunits 104 and any number of remote units 108 a-n.

The DAS 102 can communicate signals to and from terminal devices via theunit 104 and the wideband remote units 108 a-n that service one or morecoverage zones. The unit 104 can be communicatively coupled with thebase station 101 and the wideband remote units 108 a-n in any suitablemanner. Communicatively coupling devices in a DAS 102 or othertelecommunication system can involve establishing, maintaining, orotherwise using a communication link (e.g., a cable, an optical fiber, awireless link, etc.) to communicate information between the devices. Anysuitable types of communication links can be used in the DAS 102. Asuitable communication link can be a wired connection or a wirelessconnection. Types of wired connections can include, for example, aconnection via a copper cable, an optical fiber, or another suitablecommunication medium. Types of wireless connections can include, forexample, a wireless RF communication link or a microwave link. The typeof communication link between the base station 101 and the unit 104 canbe the same as or different from the type of communication link betweenthe unit 104 and the wideband remote units 108 a-n.

The unit 104 can provide downlink signals from the base station 101 tothe wideband remote units 108 a-n and receive uplink signals from thewideband remote units 108 a-n to be provided to the base station 101.Downlink signals can include signals provided from the base station 101and transmitted by the wideband remote units 108 a-n in coverage zones.Uplink signals can include signals transmitted by terminal devices andreceived by the wideband remote units 108 a-n.

The wideband remote units 108 a-n can provide signal coverage in one ormore coverage zones. Providing signal coverage in the coverage zones caninclude wirelessly transmitting downlink signals received from the unit104 to terminal devices in the coverage zones. Providing signal coveragein the coverage zones can also include wirelessly receiving uplinksignals from the mobile communication devices or other terminal devicesin the coverage zones. The wideband remote units 108 a-n can transmitthe uplink signals to the unit 104. The unit 104 can transmit the uplinksignals to the base station 101.

Although FIG. 1 depicts direct links between the unit 104 and thewideband remote units 108 a-n, other implementations are possible. Insome aspects, the unit 104 can be communicatively coupled to thewideband remote units 108 a-n via one or more extension units or otherintermediate devices.

The unit 104 can combine uplink transmissions received from some or allof the wideband remote units 108 a-n into a combined uplink signal, suchas a composite signal. A transmitter of the unit 104 can transmit thecombined uplink signal to an uplink receiver of the base station 101.The unit 104 can use the processing module 106 to combine uplinktransmissions received from the wideband remote units 108 a-n. Theprocessing module 106 can include one or more devices configured toselect uplink signals for a combination, programming instructionsexecutable by a processor to select uplink signals for a combination, orany suitable combination thereof.

In some aspects, the wideband remote units 108 a-n can operate using areduced amount of RF circuitry as compared to conventional remote units.Reducing the amount of circuitry in a remote unit can reduce one or moreof the size of the remote unit and the costs associated withmanufacturing or installing the remote unit. The amount of circuitryused in a remote unit can be reduced by, for example, using a single RFtransceiver that is configured for digitizing signals having frequencieswithin large frequency bandwidths for digital transport to a unit 104 orother head-end unit. The amount of circuitry used in a wideband remoteunit 108 can also be reduced by, for example, omitting RF signalprocessing components such as up-conversion components, down-conversioncomponents, isolation devices, etc.

FIG. 2 is a block diagram depicting an example of a wideband remote unit108 according to one aspect. The wideband remote unit 108 can include anantenna 200, a multiple wideband RF transceivers 110, and a processingmodule 212.

The multiple wideband RF transceivers 110 can include an uplink path 201and a downlink path 203. The uplink path 201 can include a low-noiseamplifier 204, an anti-aliasing filter 206, a variable gain device 208,and an ADC 210. In some aspects, the uplink path 201 can be limited tothe devices depicted in FIG. 2. In other aspects, the uplink path 201can include additional devices other than those depicted in FIG. 2. Thedownlink path 203 can include a digital-to-analog converter (“DAC”) 214,an image filter 216, and a power amplifier 218. In some aspects, thedownlink path 203 can be limited to the devices depicted in FIG. 2. Inother aspects, the downlink path 203 can include additional devicesother than those depicted in FIG. 2.

In the uplink direction, one or more elements of the antenna 200 canreceive uplink signals. Although a single antenna 200 is depicted forillustrative purposes, other implementations are possible. In someaspects, one or more antenna elements can be used for transmittingsignals and one or more other antenna elements can be used for receivingsignals. In other aspects, one or more antenna elements can be used fortransmitting signals and receiving signals in a time-divisionmultiplexed manner.

A splitter-combiner 202 in the multiple wideband RF transceivers 110 cancommunicatively couple the downlink path 203 and the uplink path 201 toa common port that is communicatively coupled to the antenna 200. Thesplitter-combiner 202 can split downlink signals to be transmitted viathe antenna 200 from uplink signals that are received via the antenna200. The low-noise amplifier 204 can amplify the uplink signals toimprove the signal-to-noise ratio of the received uplink signals.

The anti-aliasing filter 206 can filter the received uplink signals toreduce or prevent aliasing. Aliasing can be caused by converting analoguplink signals to digital uplink signals using the ADC 210. For example,the low-noise amplifier 204 can have a high dynamic range. The highdynamic range can compensate for limited attenuation from the downlinkpath 203. The anti-aliasing filter 206 in the uplink path 201 can reduceor prevent undesired signals from aliasing into desired Nyquist zones.One example of an anti-aliasing filter 206 is a surface acoustic wave(“SAW”) filter. In some aspects, a mixer or other demodulation devicecan be included in the uplink path 201. An example of a bandwidth thatmay be used by the anti-aliasing filter 206 is 75 MHz. For sample ratesas high as 7 GHz, the anti-aliasing filter 206 can be a low-pass filterwith a cut-off frequency below 3.5 GHz, which is the limit of theNyquist zone. In another example, the anti-aliasing filter 206 can use a3.2 GHz sample rate and can have an RF input bandwidth between 30 MHzand 450 MHz.

In another example, the anti-aliasing filter 206 can use a sample rateof up to 3 GHz and can have a 2.5 GHz input bandwidth. In this example,the frequency range from 700 MHz to 1 GHz can be sampled in the firstNyquist zone, and the frequency range from 1.7 GHz to 2.2 GHz can besampled in the second Nyquist zone. The sample rate for theanti-aliasing filter 206 can be selected (e.g., 2.3 GHz) to avoidaliasing of the two frequency ranges onto the same frequency.

The ADC 210 can convert the analog uplink signal to a digital uplinksignal. The ADC 210 can digitize uplink signals in a manner that allowsfor the omission of frequency translation circuitry (e.g.,down-conversion circuitry such as a mixer and local oscillator) from theuplink path 201. In some aspects, the ADC 210 can use a sampling ratesuitable for sampling signals from a wideband spectrum. The ADC 210 maybe configured to sample analog uplink RF signals at a sufficiently highsampling rate such that high-frequency signals in a wideband spectrumare sampled at a rate greater than or equal to a Nyquist rate (e.g.,twice the frequency of the sampled analog signal). For example, awideband spectrum may include signals having frequencies up to 3.5 GHz,and the ADC 210 may use a sampling rate of 7 GHz or higher.

A wideband spectrum can include a spectrum having frequency bandsassociated with multiple types of telecommunication providers. In someaspects, the wideband behavior of the remote unit 108 can involve theremote unit 108 being non-selective such that all RF bands within thefrequency range of the remote unit 108 are processed. For example, theremote unit 108 can be implemented without using dedicated filters toisolate one or more bands. The wideband behavior of the remote unit 108can also involve the remote unit 108 processing both downlink and uplinkfrequencies rather than using one or more filters to select a downlinkfrequency band or uplink frequency band for processing.

Additionally or alternatively, the ADC 210 can digitize uplink signalsin a manner that allows for implementing the remote unit 108 withoutanalog circuitry for isolating uplink signals from downlink signals. Insome aspects, the ADC 210 can have a resolution that is suitable fordigitizing signals within a wideband spectrum that have a wide range ofsignal powers. For example, the wideband remote unit 108 may beimplemented without a duplexer or other analog devices that isolatedownlink signals transmitted to terminal devices by one or more elementsof the antenna 200 from uplink signals received from terminal devices byone or more elements of the antenna 200. The absence of a duplexer orother analog isolation devices can allow the downlink signalstransmitted by one or more elements of the antenna 200 to be received byone or more elements of the antenna 200 and provided to the uplink path201 of the wideband remote unit 108. These downlink signals received bythe antenna 200 may have a higher signal strength than uplink signalsreceived from terminal devices. Using an ADC 210 with a sufficientresolution can allow one or more digital processing devices in one ormore of the wideband remote unit 108 and the unit 104 to distinguishbetween low-power uplink signals and high-power uplink signals that bothtraverse the uplink path 201.

The resolution of the ADC 210 can be expressed in a number of bits thatcorrespond to a number of available signal power levels that can bedigitally represented. For example, an n-bit ADC 210 can be used todigitally represent 2^(n) signal power levels. The dynamic range of theADC 210 (e.g., the range of signal power levels that can be digitallyrepresented using the ADC 210) can correspond to number n of bits forthe ADC 210 and the increment between the digitally represented powerlevels. For example, for an increment of m dB per bit, the dynamic rangeof an n-bit ADC 210 is n×m dB. A sufficiently wide dynamic range of theADC 210 can allow the anti-aliasing filter 206 to digitize both uplinksignals having low signal powers and downlink signals that may leak intothe uplink path 201. One example of the ADC 210 is a delta-sigma ADC.

In some aspects, the dynamic range for the ADC can be 6.02 dB×n+1.76 dB.In other aspects involving higher bit numbers, the signal dynamic rangeimprovement may decrease (e.g., to a factor of 3 dB increasing from n=12to n=14).

The sampling rate of the ADC 210, the number of bits used by the ADC 210to express signal power levels, and a data rate of a communication link220 from the wideband remote unit 108 to the unit 104 can be related.The product of the sampling rate of the ADC 210 and the number of bitsused by the ADC 210 can be less than or equal to a data rate of a serialcommunication link 220 used to communicate digital uplink signals to theunit 104. For example, the ADC 210 may sample values from an analoguplink signal at a rate of r samples per second. The ADC can encode eachsampled value using n bits. Communicating n-bit samples at a rate of rsamples per second can involve using a communication link 220 having adata rate of r×n bits per second.

The following non-limiting example illustrates (without limitation) asample configuration for the wideband remote unit 108. With respect tothe sampling frequency of the wideband remote unit 108, the widebandremote unit 108 may be used to receive uplink signals in frequency bandsfrom 200 MHz to 3 GHz. The anti-aliasing filter 206 can have a low passcorner frequency of 3 GHz with a stop-band frequency of 4 GHz. The ADC210 can be configured to digitally represent the bandwidth of 3.5 GHzthat accounts for the uplink frequency bands and the stop-band frequencyby using a sampling rate of at least 7 GHz (e.g., double the highestfrequency of 3.5 GHz). With respect to the dynamic range of the widebandremote unit 108, the signal powers of uplink signals received by thewideband remote unit 108 may be as low as −105 dBm. The signal powers ofdownlink signals transmitted by the wideband remote unit 108 may be ashigh as +12 dBm. If the downlink path 203 and the uplink path 201 arenot isolated from one another, the range of signal powers for signalstraversing the uplink path 201 (e.g., low-power uplink signals, downlinksignals received by one or more elements of the antenna 200) can be from−105 dBm to +12 dBm, for a total range of 117 dB. If an increment of 6dB is used to represent different signal power levels, the ADC 210 canuse 20 bits (117 dB divided by 6 dB per bit) to digitally representsampled signal power values of analog uplink RF signals. In some cases,the data rate for a serial communication link 220 between the widebandremote unit 108 and the unit 104 can be at least 140 Gbps (the productof the 7-GHz sampling rate and the 20-bit digital value) in the uplinkdirection. In other cases, the data rate for the serial communicationlink 220 can be reduced further using filtering and sample rateconversion.

In the downlink direction, the wideband remote unit 108 can receivedigital downlink signals from the unit 104. For example, a digitalsignal representing a downlink frequency band can be provided to a DAC214 of the wideband remote unit 108 via a serial communication link froma unit 104.

The digital downlink signals can be converted to analog RF downlinksignals by the high-speed DAC 214. The DAC 214 can generate RF signalswithout performing frequency translation in the analog domain usingfrequency translation circuitry (e.g. up-conversion circuitry such as amixer and local oscillator in the downlink path 203). In some aspects,frequency translation may be performed in the digital domain usinghigh-speed digital circuitry in the DAC 214. In additional oralternative aspects, frequency translation may be performed in thedigital domain using a processing module 212.

The image filter 216 can filter the RF downlink signals to remove imagesgenerated by the DAC 214. The DAC 214 may create images as a result ofthe sample-and-hold operation performed by the DAC 214. The image filter216 that removes or reduces these images can be an image rejectionanalog filter in the downlink path 203.

The RF downlink signals can be amplified by the power amplifier 218 fortransmission to one or more terminal devices.

In some aspects, the wideband remote unit 108 can include a singlewideband RF transceiver 110 that is configured to receive and transmitsignals at frequencies within all frequency bands of interest for a DAS102. In other aspects, a wideband remote unit 108 can include multiplewideband RF transceivers 110. Each of the wideband RF transceivers 110can receive and transmit signals at frequencies within a portion of thefrequency bands of interest for a DAS 102. For example, a first widebandRF transceiver in the wideband remote unit 108 can transmit or receivesignals having frequencies in a frequency band of 200 MHz to 1 GHz, asecond wideband RF transceiver in the wideband remote unit 108 cantransmit or receive signals having frequencies in a frequency band of 1GHz to 2 GHz, and a third wideband RF transceiver in the wideband remoteunit 108 can transmit or receive signals having frequencies in afrequency band of 2 GHz to 3 GHz.

The wideband remote unit 108 can include simplified circuitry ascompared to an RF transceiver of a conventional remote unit. In someaspects, the wideband remote unit 108 can omit circuitry used forfrequency translation that would otherwise be performed in one or bothof the uplink path 201 and the downlink path 203 (e.g., up-conversioncomponents, down-conversion components, amplifiers used to compensatefor loss introduced by frequency translation, etc.). For example,conventional remote units of a DAS may include a large amount of RF,analog, and digital circuitry, such as a downlink path 203 and an uplinkpath 201 having multiple RF processing components. The downlink path 203can include up-conversion circuitry (e.g., a local oscillator and amixer) to up-convert downlink signals from IF to RF and a filter andamplifier following the up-conversion circuitry. The uplink path 201 caninclude a bandpass filter, down-conversion circuitry (e.g., a localoscillator and a mixer) to down-convert uplink signals from RF to IF,and one or more amplifiers following the down-conversion circuitry.

The RF, analog, and digital circuitry of a conventional remote unit mayuse a large amount of power. For example, the mixers in the uplink anddownlink paths 203 can respectively attenuate uplink and downlinksignals. The amplifiers following the mixers in the uplink and downlinkpaths 203 can compensate for the loss introduced by the mixers. Other RFsignal processing components, such as anti-aliasing filters, can be usedto compensate for non-linear distortion of uplink and downlink signalsintroduced by the up-conversion and down-conversion circuitry. The useof the amplifiers and filters associated with up-conversion componentsand down-conversion components can increase one or more of the powerused by a remote unit, the size of the remote unit, the costs associatedwith manufacturing or installing the remote unit, etc. The inclusion ofthe RF, analog, and digital circuitry may also increase the physicaldimensions of the remote unit, thereby increasing the amount of spacerequired to install the remote unit in a deployment environment (e.g., abuilding serviced using the DAS 102).

In some aspects, the wideband remote unit 108 can be implemented withouta duplexer. For example, a conventional RF transceiver may include oneor more duplexers for isolating a transmitter output (e.g., downlinksignals) from a receiver input (e.g., uplink signals). The duplexer canallow frequencies within the downlink frequency band to be provided fromthe transmitter output to the antenna and can allow frequencies withinthe uplink frequency band to be provided from the antenna output to thereceiver. Isolating a transmitter output from a receiver input canprevent downlink signals from interfering with uplink signals. Theduplexer may introduce some amount of insertion loss, which can causesome of the power amplification from the power amplifier to be wasted.The waste of power amplification can reduce the efficiency ofconventional remote units.

FIG. 3 is a block diagram depicting an example of the processing module212 of the wideband remote unit 108 according to one aspect. Theprocessing module 212 can include one or more suitable processingdevices that can be used to implement a digital processing section. Theprocessing module 212 can perform one or more operations on downlinksignals received from a unit 104. The processing module 212 can alsoperform one or more operations on uplink signals to be provided to theunit 104. Examples of a processing device include anapplication-specific integrated circuit (“ASIC”), a field-programmablegate array (“FPGA”), or another suitable processing device or suitableprocessing circuitry.

The processing module 212 can include a parallel-serial converter 302, aframer-deframer 304, and a digital pre-distortion module 306. In someaspects, one or more of the parallel-serial converter 302, theframer-deframer 304, and the digital pre-distortion module 306 caninclude one or more hardware devices included in or communicativelycoupled to a processing device of the processing module 212. Inadditional or alternative aspects, one or more of the parallel-serialconverter 302, the framer-deframer 304, and the digital pre-distortionmodule 306 can include program code stored in a memory device andexecuted by a processing device of the processing module 212. Inadditional or alternative aspects, one or more of the parallel-serialconverter 302, the framer-deframer 304, and the digital pre-distortionmodule 306 can be implemented using a combination of one or morehardware devices included in or communicatively coupled to a processingdevice of the processing module 212 and program code stored in a memorydevice and executed by a processing device of the processing module 212.

In a downlink direction, the parallel-serial converter 302 can performone or more operations to de-serialize a serial downlink data streaminto multiple digital downlink signals to be provided to differentdownlink paths 203 of the wideband remote unit 108. For example, theparallel-serial converter 302 can de-multiplex digital downlink signalsfrom a common serial downlink data stream. In an uplink direction, theparallel-serial converter 302 can perform one or more operations toserialize parallel uplink signals into a common serialized uplink datastream to be provided to the unit 104. For example, the parallel-serialconverter 302 can combine parallel uplink digital signals received frommultiple uplink signal paths of the remote 108 into a serialized uplinksignals.

In additional or alternative aspects, the transport between the unit 104and one or more of the ADC 210 and the DAC 214 can use an internalformat for the ADC 210 and the DAC 214, which can be transported eitheras-is or with framing by the framer-deframer 304. In these aspects, theparallel-serial converter 302 can be omitted.

In additional or alternative aspects, a regenerating serial data linkrepeater can be included to restore the bits to meet the timing that isused by the DAC 214 or the unit 104. In a downlink direction, theframer-deframer 304 can de-frame digital downlink signals to obtaindownlink payload data for transmission via the antenna 200. In an uplinkdirection, the framer-deframer 304 can frame digital uplink signals fortransmission to the unit 104.

In some aspects, the digital pre-distortion module 306 can pre-distortdownlink signals prior to digital-to-analog conversion and transmissionvia the antenna 200. Pre-distorting downlink signals prior totransmission via the antenna 200 can reduce or prevent downlinkintermodulation products from being generated in the downlink path 203.For example, one or more components of the downlink path 203 orelsewhere in the remote unit 108 can include non-linearities thatgenerate intermodulation products. The digital pre-distortion module 306can pre-distort downlink signals in a manner that offsets or otherwisecompensates for these non-linearities. Offsetting or otherwisecompensating for these non-linearities can prevent intermodulationproducts from being transmitted by the remote unit 108 or reduce theintermodulation products received in the uplink path 201. In additionalor alternative aspects, the digital pre-distortion module 306 canpre-distort digital uplink signals prior to transmission to the unit104. Pre-distorting uplink signals prior to transmission via the antenna200 can reduce or prevent uplink intermodulation products from beinggenerated in an uplink path to the unit 104. In some aspects, thispredistortion can address the intermodulation products generated fromone or more of intra-band signal combinations and interbandcombinations.

In other aspects, the wideband remote unit 108 may be implemented withhighly linear stages, such that the digital pre-distortion module 306may be omitted.

The processing module 212 can be used to prepare digital signals fortransport via the DAS 102. In the uplink path 201, the processing module212 can extract frequency channels of interest and can suppress orremove unwanted signals in the uplink path 201. In the downlink path203, the digital processing circuit can shift frequency channels orbands of interest to a desired digital frequency prior to downlinksignals being provided to the DAC 214.

In some aspects, the processing module 212 depicted in FIG. 3 can beomitted from the wideband remote unit 108 and the unit 104 can include aprocessing module for performing the digital signal processing describedabove. For example, FIG. 4 is a block diagram depicting an example of aunit 104. The unit 104 can include a downlink signal processing section402, a non-duplexer isolation sub-system 404, and an uplink signalprocessing section 406. The downlink signal processing section 402 canperform one or more operations for removing unwanted signals and noisefrom downlink signals. The uplink signal processing section 406 canperform one or more operations for removing unwanted signals and noisefrom uplink signals.

Using the unit 104 to remove unwanted signals and noise can allow for areduction in one or more of the size, power requirements, and costs ofmanufacturing or installing wideband remote units 108 a-n. The widebandremote units 108 a-n can perform functions such as transmitting downlinksignals, receiving the uplink signals, and communicating uplink anddownlink signals with other units in the DAS 102 without performingoperations for removing unwanted signals and noise.

In some aspects, the bandwidth of communication links between widebandremote units 108 a-n and a unit 104 can be sufficient to accommodatesignals within a large dynamic range. One example of such a bandwidth is140 Gbps. For example, a DAS 102 using frequency division duplexing(“FDD”) or time division duplexing (“TDD”), digital filtering can beused to filter downlink signals from the uplink path 201, therebyreducing the amount of transport bandwidth that is used in the uplinkpath 201. Adaptive filtering techniques can also be used to canceldownlink signals from the uplink path 201 to reduce the uplink transportbandwidth over the uplink serial link.

The non-duplexer isolation sub-system 404 can mitigate, cancel, filter,or otherwise attenuate downlink signals or other interfering signalstraversing an uplink path 201 from the wideband remote unit. Examples ofother interfering signals include intermodulation products generated bydownlink signals traversing the downlink path 203 that may fall into theuplink frequency band. The non-duplexer isolation sub-system 404 canallow duplexers to be omitted from the remote units 108 a-n. Anysuitable implementation can be used for the non-duplexer isolationsub-system 404, such as, for example, one or more configurable filters,one or more signal cancellation sub-systems, etc.

In some aspects, the non-duplexer isolation sub-system 404 may includeone or more configurable filters. For example, FIG. 5 is a block diagramdepicting an example of a non-duplexer isolation sub-system 404 thatincludes one or more configurable filters 506 according to one aspect.The configurable filter 506 may be positioned in the uplink path 504 ofthe unit 104. The configurable filter 506 can reject or otherwiseattenuate spurious downlink signals or other interfering signals fromthe downlink path 502 that may leak into, or otherwise be present in,the uplink path 504. The spurious downlink signals or other interferingsignals can be attenuated with respect to a combined uplink signalgenerated by a combiner 508 of the unit 104. The combiner 508 can beimplemented in hardware, in program code executed by a suitableprocessing device (e.g., an FPGA, an ASIC, etc.), or some combinationthereof. The combiner 508 can combine uplink signals from multiplewideband remote units 108 a-n. For example, the unit 104 can combineuplink signals received from terminal devices via the remote units 108a-n and filter or otherwise attenuate spurious downlink signals or otherinterfering signals. The unit 104 can transmit the combined uplinksignal to the base station 101.

In additional or alternative aspects, spurious signals generated fromthe DAC 214 can be prevented from leaking into the uplink band (orreduced in the uplink band) by adjusting the sampling clock frequency ofthe DAC 214. For example, the sampling clock frequency of the DAC 214can be adjusted to a frequency that causes the ADC 210 to move spuriousdownlink signals in the uplink path 201 outside of the relevantfrequency band relevant for uplink traffic. The adjustment can beperformed for one or more of the remote units 108 a-n. The adjustmentcan be performed based on the uplink frequencies in use and the spuriousproducts generated by the downlink path 203. A re-sampling block in theprocessing module 212 can be used to adjust the clock rates of in one ormore of the remote units 108 a-n if a common sampling rate is used.

In additional or alternative aspects, the phasing of the sampling clockof the ADC 210 can be modified with respect to the clock of the DAC 214.The adjustment in phase can minimize the probability of peaks at themoment of sampling. This phasing can avoid or reduce periodic signalpeaking by adjusting the sample clock phase to be minimize theoccurrence of peaks when sampling.

Although FIG. 5 depicts the combiner 508 as following the configurablefilter 506 in the uplink path 504, other implementations are possible.For example, spurious downlink signals or other interfering signals fromthe wideband remote unit 108 a can be combined with transmissions fromother wideband remote units 108 b-n, and the configurable filter 506 canbe used to filter the combined uplink signal to remove or otherwiseattenuate spurious downlink signals or other interfering signals.

In some aspects, the configurable filter 506 can be configured via oneor more mechanical steps that select a frequency response for theconfigurable filter 506. In other aspects, the configurable filter 506can be configured electronically by a control signal that configures aprocessor to select a frequency response for a configurable filter 506implemented digitally. In other aspects, the configurable filter 506 canbe configured electronically by an applied voltage or current signalthat can modify a frequency response for a configurable filter 506implemented using varactor diodes.

In additional or alternative aspects, the non-duplexer isolationsub-system 404 can include circuitry capable of performing activemitigation of undesirable signals. Mitigating an undesirable signal caninclude cancelling the undesirable signal or otherwise minimizing theundesirable signal. For example, FIG. 6 is a block diagram depicting anexample of a non-duplexer isolation sub-system 404 that includes acancellation sub-system according to one aspect. The cancellationsub-system can include a coupler 602, a cancellation signal generator604, and a combiner 606. The cancellation sub-system depicted in FIG. 6can be used in combination with or as an alternative to the configurablefilter 506 depicted in FIG. 5.

The coupler 602 can sample a downlink signal traversing the downlinkpath 502. The cancellation signal generator 604 can adjust the gain andshift the phase of the sampled downlink signal to generate acancellation signal or other mitigation signal. The cancellation signalor other mitigation signal can be summed or otherwise combined with thesignal traversing the uplink path 504 using a combiner 606. Combiningthe cancellation signal or other mitigation signal with the signaltraversing the uplink path 504 can mitigate undesirable signalcomponents (e.g., spurious downlink signals or other interferingsignals) in the signal traversing the uplink path 504.

In some aspects, the cancellation signal generator 604 can includeanalog filters that generate the cancellation signal or other mitigationsignal. In additional or alternative aspects, the cancellation signalgenerator 604 can include analog filters that generate the cancellationsignal or other mitigation signal. In some aspects, the analog ordigital filters are adaptive filters that can adjust a frequencyresponse dynamically. In other aspects, the analog or digital filtersare non-adaptive filters that are configured to have a static frequencyresponse that may be configured manually.

Although FIG. 6 depicts the combiner 508 as following the combiner 606in the uplink path 504, other implementations are possible. For example,spurious downlink signals or other interfering signals from the widebandremote unit 108 a can be combined with transmissions from other widebandremote units 108 b-n, and a cancellation signal or other mitigationsignals can be summed or otherwise combined with the combined uplinksignal to remove or otherwise attenuate spurious downlink signals orother interfering signals in the combined uplink signal.

FIG. 7 is a block diagram depicting another example of a non-duplexerisolation sub-system 404 that includes an attenuation sub-system. Theattenuation sub-system can include a coupler 702 that is communicativelycoupled to the downlink path 502, a correlator 706, a coupler 706 thatis communicatively coupled to the uplink path 504, and an attenuator708. In various aspects, one or more of the couplers 702, 706, thecorrelator 706, and the attenuator 708 can be implemented as hardwaredevices, as program code executed by a processing device of the unit104, or some combination thereof.

The coupler 702 can sample signals traversing the downlink path 502. Thecoupler 706 can sample signals traversing the uplink path 504. Thecorrelator 704 can determine whether a signal traversing the downlinkpath 502 is correlated with a signal traversing the uplink path 504. Acorrelation between the signal traversing the downlink path 502 and thesignal traversing the uplink path 504 can indicate that the signaltraversing the uplink path 504 is a leaked downlink signal. Thecorrelator 704 can respond to identifying the correlation by configuringthe attenuator 708 to attenuate, mute, or otherwise exclude the signaltraversing the uplink path 504 from a combined signal generated by thecombiner 508.

Although FIG. 6 depicts the combiner 508 as following the attenuator 708in the uplink path 504, other implementations are possible. Theattenuation sub-system depicted in FIG. 7 can be used in combinationwith or as an alternative to one or more of the configurable filter 506depicted in FIG. 5 and the cancellation sub-system depicted in FIG. 6.For example, a correlator 704 can be used to trigger or otherwisecontrol the operation of the cancellation signal generator 604. Thecorrelator 704 can correlate a downlink signal traversing the downlinkpath 502 with a signal component of a signal traversing the uplink path504. A processing device can configure the cancellation signal generator604 to generate a cancellation signal based on correlating the downlinksignal traversing the downlink path 502 with the signal component of asignal traversing the uplink path 504. The combiner 606 can combine thecancellation signal with a combined uplink signal traversing the uplinkpath 504. In some aspects, a detected correlation can cause thecancellation signal generator 604 to be activated such that subsequentinterfering downlink components can be cancelled from signal traversingthe uplink path 504. For example, at a first point in time, a detectedcorrelation between a first downlink signal in the downlink path 502 anda first signal component in the uplink path 504 can be subsequently usedto generate a cancellation signal for cancelling, at a second point intime, a second signal component in the uplink path 504 corresponding toa second downlink signal in the downlink path 504.

In additional or alternative aspects, the non-duplexer isolationsub-system 404 or another suitable sub-system can cancel or otherwiseattenuate intermodulation products generated by the remote unit 108.Such a sub-system can be implemented in a manner similar to the examplesdepicted in FIGS. 5 and 6. For example, in some aspects, a coupler canbe positioned at the output of a power amplifier in the remote unit 108.A signal sampled using the coupler can include intermodulation productsgenerated by the remote unit 108. The sampled signal can be used by acancellation signal generator to generate a cancellation or othermitigation signal for suppressing the intermodulation products in theuplink path. In additional or alternative aspects, a non-linear modelfor the transmit chain (e.g., a DAC and power amplifier in the downlinkpath) can be used by a processing device to estimate or otherwise modelintermodulation products generated by the remote unit 108. Thenon-linear model can be used to identify and suppress intermodulationproducts in the uplink path (e.g., through cancellation or attenuationof the intermodulation products).

In some aspects, the DAC 214 of the wideband remote unit 108 may have asin(x)/x response. For example, FIG. 8 is a graph 800 depicting anexample of frequency response 802 associated with a wideband remote unit108. The wideband remote 108 can use a compensation digital filter toamplify high frequency content that can be attenuated by the sin(x)/xresponse. The digital filtering can be performed by the DAC 214, by aprocessing device in the processing module 212, by an analog filterfollowing the DAC 214 in the downlink path 203, or by any other suitablecomponent. The example of a sin(x)/x response 802 depicted in FIG. 8 isassociated with a 214 DAC that uses a sampling rate of 7 gigasamples persecond. FIG. 8 also depicts a compensation 804 for the loss in gain fromthe sin(x)/x response that can be provided by a compensation filter.

In some aspects, a DAS 102 having wideband remote units 108 a-n cansupport Multiple-Input Multiple-Output (“MIMO”) communication. Thewideband remote units 108 a-n can be deployed on a smaller grid thanconventional remote units. For example, a conventional remote unit mayservice a grid of 100 feet (or approximately 30 meters) covering 10,000square feet (or approximately 900 square meters). A wideband remote unit108 may service a grid of 30 feet (or approximately 10 meters) covering900 square feet (or approximately 100 square meters). These numbers areprovided for illustrative purposes only; other distance and coverageareas may be applicable. Reducing a grid size can reduce a requiredamount of transmit power in the downlink direction. The spacing ofwideband remote units 108 a-n for MIMO operation can be selected basedon a required grid size required for the DAS 102.

FIG. 9 is a diagram depicting an example of wideband remote unitsdeployed in a configuration 900 that can be used for MIMO operationaccording to one aspect. For example, the wideband remote units 108 canbe built into or otherwise coupled to ceiling tiles 902. Other examplesof structures into which the wideband remote units 108 can be built orto which the wideband remote units 108 can be coupled include lightfixtures, power outlets, smoke or fire detectors, etc. The widebandremote units 108 can be used for MIMO operation. The wideband remoteunits 108 can be spaced apart from one another such that adjacentwideband remote units 108 can be used in a MIMO configuration. Forexample, as depicted in FIG. 9, the sixteen wideband remote units 108a-n are grouped into four sets of four wideband remote units 108 a-n toprovide a four-by-four MIMO configuration. The MIMO streams can begenerated at the unit 104. The unit 104 can synchronize the MIMO streamsin time such that a set or subset of the remote units 108 a-n configuredfor MIMO operation can transmit MIMO streams simultaneously ornear-simultaneously.

The DAS 102 can be configured to determine the proximity of a givenwideband remote unit 108 to other wideband remote units 108.Triangulation or some intelligent method of determining relative spacingbetween wideband remote units 108 can be used to identify which widebandremote units 108 are to be used in a MIMO configuration. The powerlevels of the identified wideband remote units 108 can be adjusted tocompensate for path loss.

In some aspects, the wideband remote units 108 can adaptively changefrom MIMO operation to single-input/single-output (“SISO”) operation incases where low multi-path is experienced in the particularinstallation.

In additional or alternative aspects, the use of wideband remote units108 in a DAS 102 can facilitate public safety features. For example,using a wideband remote unit 108 that services a smaller grid (e.g., 10square feet) can allow for more precise geolocation of a terminal device(e.g., a mobile phone) than a conventional remote unit that services alarger grid (e.g., 100 square feet) employing proximity detection as anexample. In some aspects, a unit 104 that receives uplink signals canidentify a given uplink signal as being received at a given widebandremote unit 108 (or group of wideband remote units 108) prior tocombining the uplink signal with other uplink signals. In other aspects,a processing device in a wideband remote unit 108 may implement ameasurement receiver function that is used to determine the signalstrength of uplink signals received from a given terminal device. Thewideband remote unit 108 can notify other units in the DAS 102 that theterminal device is located in close proximity to the wideband remotebased on the signal strength of the uplink signal exceeding a specifiedthreshold.

FIG. 10 is a flow chart depicting an example of a process 1000 for usinga wideband remote unit from FIG. 1 to obtain wideband uplink data fortransmission to a base station according to one aspect. The process 1000is described with respect to one or more of the aspects and examplesdescribed above with respect to FIGS. 1-9. Other implementations,however, are possible.

The process 1000 involves receiving wideband signals including uplink RFsignals and leaked downlink RF signals, as depicted in block 1002. Forexample, one or more of the wideband remote units 108 a-n can receivewideband signals, as described above with respect to one or more of theexamples in FIGS. 1-3. A wideband remote unit 108 can receive thewideband signals via an uplink path 201 that is communicatively coupledto one or more antennas 200. Uplink RF signals can include signalsreceived by the wideband remote unit 108 from terminal devices. In someaspects, uplink RF signals can have uplink signal powers at or near anoise level (e.g. the thermal noise level) associated with the widebandremote unit (e.g., noise generated by the antenna 200). Leaked downlinkRF signals can include signal power from one or more downlink RF signalstraversing a downlink path 203 of the wideband remote unit 108 andtransmitted using one or more elements of the antenna 200 of thewideband remote unit 108.

The process 1000 also involves converting the wideband RF signals todigital RF signals, as depicted in block 1004. For example, one or moreof the wideband remote units 108 a-n can convert received wideband RFsignals into digital RF signals to be provided to a unit 104, asdescribed above with respect to one or more of the examples in FIGS. 2and 3.

In some aspects, a wideband remote unit 108 can include an ADC 210having a dynamic range suitable for digitizing uplink signals with lowsignal powers and leaked downlink signals with high signal powers, asdescribed above with respect to FIG. 2. For example, a dynamic range ofthe ADC 210 can have a minimum value corresponding to the noise leveland a maximum value corresponding to the downlink signal power ofdownlink signals transmitted by the wideband remote unit 108. In someaspects, the dynamic range of the ADC 210 can be based on or otherwisecorrespond to a data rate of the communication link 220, as describedabove with respect to FIG. 2.

In additional or alternative aspects, the ADC 210 can be configured witha sampling rate that corresponds to a maximum RF frequency of thewideband signals. For example, as described above with respect to FIG.2, the sampling rate of the ADC 210 can be twice the frequency of amaximum RF frequency of the wideband spectrum received by the remoteunit 108. In some aspects, the sampling rate of the ADC 210 can beconfigured based on one or more of a dynamic range of the ADCs and adata rate of the communication link 220, as described above with respectto FIG. 2.

The process 1000 also involves providing the digital RF signals from aremote unit to a unit in communication with a base station, as depictedin block 1006. For example, one or more of the wideband remote units 108a-n can transmit the digital RF signals generated from the receivedwideband RF signals to the unit 104 via a communication link 220, asdescribed above with respect to one or more of the examples in FIGS. 2and 3.

The process 1000 also involves mitigating the digital RF signalscorresponding to the leaked downlink RF signals in a combined uplinksignal to be transmitted to the base station, as depicted in block 1008.For example, the unit 104 can use the non-duplexer isolation sub-system404 to filter, exclude, cancel, attenuate, or otherwise mitigatespurious signals from a combined uplink signal, as described above withrespect to one or more of the examples in FIGS. 4-7. In some aspects,one or more devices of the unit 104 (e.g., the non-duplexer isolationsub-system 404) can filter a digital RF signal (e.g., a digital signalcorresponding to a leaked downlink signal) from a combined uplink signalgenerated using one or more uplink signals (e.g., another digital RFsignal corresponding to an uplink RF signal received by the remote unit108. In additional or alternative aspects, one or more devices of theunit 104 (e.g., the non-duplexer isolation sub-system 404) can cancel orotherwise mitigate a digital RF signal (e.g., a digital signalcorresponding to a leaked downlink signal) from a combined uplink signalgenerated using one or more uplink signals (e.g., another digital RFsignal corresponding to an uplink RF signal received by the remote unit108. In additional or alternative aspects, one or more devices of theunit 104 (e.g., the non-duplexer isolation sub-system 404) can mute orotherwise attenuate a digital RF signal (e.g., a digital signalcorresponding to a leaked downlink signal) from a combined uplink signalgenerated using one or more uplink signals (e.g., another digital RFsignal corresponding to an uplink RF signal received by the remote unit108.

While the present subject matter has been described in detail withrespect to specific aspects and features thereof, it will be appreciatedthat those skilled in the art, upon attaining an understanding of theforegoing may readily produce alterations to, variations of, andequivalents to such aspects and features. Each of the disclosed aspects,examples, and features can be combined with one or more of the otherdisclosed aspects, examples, and features. Accordingly, it should beunderstood that the present disclosure has been presented for purposesof example rather than limitation, and does not preclude inclusion ofsuch modifications, variations, and/or additions to the present subjectmatter as would be readily apparent to one of ordinary skill in the art.

What is claimed is:
 1. A wideband remote unit of a distributive antennasystem, the wideband remote unit comprising: a downlink path, whereinthe wideband remote unit is configured to wirelessly transmit a downlinkRF signal received from a base station via a unit of the distributiveantenna system in communication with the base station; and a widebanduplink path that transmits in an uplink direction to the unit of thedistributive antenna system a signal comprising a digital representationof an uplink RF signal wirelessly received from a user by the widebandremote unit and a digital representation of a leaked downlink RF signal,wherein the leaked downlink RF signal includes signal power from thedownlink RF signal that has leaked into the wideband uplink path; and aconverter in the wideband uplink path that receives both the uplink RFsignal and the leaked downlink RF signal, wherein the convertergenerates the signal comprising the digital representation of the uplinkRF signal and the digital representation of the leaked downlink RFsignal by processing both the uplink RF signal and the leaked downlinkRF signal; wherein the converter comprises at least oneanalog-to-digital converter configured with a sampling ratecorresponding to a maximum RF frequency of a composite uplink signal anda data rate for a digital communication link.
 2. The wideband remoteunit of claim 1, wherein the converter is configured with a dynamicrange suitable to digitize both the uplink RF signal and the leakeddownlink RF signal.
 3. The wideband remote unit of claim 1, furthercomprising a splitter-combiner configured to couple to an antenna;wherein an output of the downlink path is coupled to thesplitter-combiner; wherein an input of the wideband uplink path iscoupled to the splitter-combiner; and wherein the leaked downlink RFsignal is leaked into the wideband uplink path via thesplitter-combiner.
 4. A wideband remote unit of a distributive antennasystem, the wideband remote unit comprising: a downlink path, whereinthe wideband remote unit is configured to wirelessly transmit a downlinkRF signal received from a base station via a unit of the distributiveantenna system in communication with the base station; and a widebanduplink path that transmits in an uplink direction to the unit of thedistributive antenna system a signal comprising a digital representationof an uplink RF signal wirelessly received from a user by the widebandremote unit and a digital representation of a leaked downlink RF signal,wherein the leaked downlink RF signal includes signal power from thedownlink RF signal that has leaked into the wideband uplink path; and aconverter in the wideband uplink path that receives both the uplink RFsignal and the leaked downlink RF signal, wherein the convertergenerates the signal comprising the digital representation of the uplinkRF signal and the digital representation of the leaked downlink RFsignal by processing both the uplink RF signal and the leaked downlinkRF signal; wherein an uplink signal power of the uplink RF signal has athermal noise level associated with the wideband remote unit, whereinthe converter comprises an analog-to-digital converter, wherein adynamic range of the converter is a function of a dynamic range of theanalog-to-digital converter, wherein a minimum value of the dynamicrange of the converter corresponds to the thermal noise level and amaximum value of the dynamic range of the converter corresponds to adownlink signal power of the downlink RF signal.
 5. A distributedantenna system comprising: a first unit of the distributed antennasystem in communication with a base station; a second unit of thedistributed antenna system in communication with the first unit, thesecond unit comprising: a downlink path, wherein the second unit isconfigured to wirelessly transmit a downlink RF signal received from thebase station via the first unit of the distributed antenna system; and awideband uplink path that transmits in an uplink direction to the firstunit of the distributed antenna system a signal comprising a digitalrepresentation of an uplink RF signal wirelessly received from a user bythe second unit and a digital representation of a leaked downlink RFsignal, wherein the leaked downlink RF signal includes signal power fromthe downlink RF signal that has leaked into the wideband uplink path;wherein the second unit further comprises: a converter in the widebanduplink path that receives both the uplink RF signal and the leakeddownlink RF signal, wherein the converter generates the signalcomprising the digital representation of the uplink RF signal and thedigital representation of the leaked downlink RF signal by processingboth the uplink RF signal and the leaked downlink RF signal; wherein adynamic range of the converter is based on a data rate for a digitalcommunication link between the first unit and the second unit.
 6. Thedistributed antenna system of claim 5, wherein the second unit furthercomprises a splitter-combiner configured to couple to an antenna;wherein an output of the downlink path is coupled to thesplitter-combiner; wherein an input of the wideband uplink path iscoupled to the splitter-combiner; and wherein the leaked downlink RFsignal enters the wideband uplink path via the splitter-combiner.
 7. Thedistributed antenna system of claim 5, wherein the converter isconfigured with a dynamic range suitable to digitize both the uplink RFsignal and the leaked downlink RF signal.
 8. The distributed antennasystem of claim 5, wherein the first unit comprises a non-duplexerisolation sub-system configured to mitigate the digital representationof the leaked downlink RF signal.
 9. The distributed antenna system ofclaim 5, wherein the first unit is configured to mitigate the digitalrepresentation of the leaked downlink RF signal by at least one of:filtering the digital representation of the leaked downlink RF signalfrom a wideband composite uplink signal; cancelling the digitalrepresentation of the leaked downlink RF signal from the widebandcomposite uplink signal; or attenuating the digital representation ofthe leaked downlink RF signal.
 10. The distributed antenna system ofclaim 5, wherein the first unit is configured to mitigate the digitalrepresentation of the leaked downlink RF signal by: correlating adownlink signal traversing the downlink path with a signal componenttraversing the wideband uplink path; generating a cancellation signalcorresponding to the digital representation of the leaked downlink RFsignal based on correlating the downlink signal traversing the downlinkpath with the signal component traversing the wideband uplink path; andcombining the cancellation signal with a combined uplink signalgenerated from the digital representation of the uplink RF signal.
 11. Adistributed antenna system comprising: a first unit of the distributedantenna system in communication with a base station; a second unit ofthe distributed antenna system in communication with the first unit, thesecond unit comprising: a downlink path, wherein the second unit isconfigured to wirelessly transmit a downlink RF signal received from thebase station via the first unit of the distributed antenna system; and awideband uplink path that transmits in an uplink direction to the firstunit of the distributed antenna system a signal comprising a digitalrepresentation of an uplink RF signal wirelessly received from a user bythe second unit and a digital representation of a leaked downlink RFsignal, wherein the leaked downlink RF signal includes signal power fromthe downlink RF signal that has leaked into the wideband uplink path;wherein the second unit further comprises: a converter in the widebanduplink path that receives both the uplink RF signal and the leakeddownlink RF signal, wherein the converter generates the signalcomprising the digital representation of the uplink RF signal and thedigital representation of the leaked downlink RF signal by processingboth the uplink RF signal and the leaked downlink RF signal; wherein anuplink signal power of the uplink RF signal has a thermal noise levelassociated with the second unit, wherein the converter comprises ananalog-to-digital converter, wherein a dynamic range of the converter isa function of a dynamic range of the analog-to-digital converter,wherein a minimum value of the dynamic range of the convertercorresponds to the thermal noise level and a maximum value of thedynamic range of the converter corresponds to a downlink signal power ofthe downlink RF signal.
 12. The distributed antenna system of claim 11,wherein the analog-to-digital converter has a sampling ratecorresponding to a maximum RF frequency of a wideband composite uplinksignal and a data rate for a digital communication link.
 13. Adistributed antenna system comprising: a first unit of the distributedantenna system in communication with a base station; a second unit ofthe distributed antenna system in communication with the first unit, thesecond unit comprising: a downlink path, wherein the second unit isconfigured to wirelessly transmit a downlink RF signal received from thebase station via the first unit of the distributed antenna system; and awideband uplink path that transmits in an uplink direction to the firstunit of the distributed antenna system a signal comprising a digitalrepresentation of an uplink RF signal wirelessly received from a user bythe second unit and a digital representation of a leaked downlink RFsignal, wherein the leaked downlink RF signal includes signal power fromthe downlink RF signal that has leaked into the wideband uplink path;wherein the downlink RF signal comprises a first multiple-input,multiple-output data stream received from the first unit, wherein thedistributed antenna system further comprises: a third unit configuredto: wirelessly transmit an additional downlink RF signal comprising asecond multiple-input, multiple-output data stream, wherein anadditional leaked downlink RF signal is obtained from the additionaldownlink RF signal wirelessly transmitted by the third unit, andtransmit a third digital RF signal to the first unit, wherein the thirddigital RF signal is generated from the additional leaked downlink RFsignal, wherein the first unit is further configured to mitigate thethird digital RF signal.